Spherical bearings (also known as cup bearings) provide a cardanic or gimballed mount of a rotating part, for example of a shaft of a gear. The motion of the shaft is restricted to rotation. In order to mount the shaft in axial direction, the spherical bearing acts as a bidirectional thrust bearing allowing angular deflections between the shaft and the shaft support. For this purpose, a ball socket of the spherical bearing may be sufficiently great to surround the spherical head of the bearing. According to an alternative design, a spherical bearing may comprise two counteracting ball sockets, which limit the movement of the ball head to a rotary motion. A third commonly known design concept applies two separate spherical bearings forming a set of bearings, which limits the movement of the ball head in axial direction. The hemispheres of the two counteracting ball sockets are typically arranged to have a common center so as to allow a slight tilting between the shaft axis (ball head) and the supported element axis (bearing socket).
Spherical bearings have widespread applications. Among these, one possible application is mounting of a shaft in a planetary gear. Furthermore, planetary gears may be applied in the drive train of a wind generator (also known as a wind energy plant, a wind power plant or a wind turbine). However, in particular in planetary gears, there may be limited construction space for the bearings.